High frequency electronic apparatus



11111624, 1941. J, BLEWETT' H 2,247,U77

HIGH FREQUENCY ELECTRONIC APPARATUS Filed Ju1y27, 19,40 3 SheetsSheet'l Inventors:

Their Attorn ey.

June 24, 1941. BLEWETT ET AL 2,247,077

HIGH FREQUENCY ELECTRONIC APPARATUS Filed July 27, 1940- s Sheets-Sheet 2 Fig" 5,

lhventorz Simon Ramo, John P. Blewett,

by W 6.

Their Attorhey.

June 9 1- J.-P. BLEWETT ETA]. 9 5077 HIGH FREQUENCY ELECTRONIC APPARATUS Filed July, 27, 1940 3 Shegts-Sheet 3 Fig.5.

Inventors: Sin'won Rarnq John F. B|ewett,-

Their Attorn e y.

I fied above.

Patented June 24, 1941 HIGH FREQUENCY ELECTRONIC APPARATUS John P. Blewett, Scotia, and Simon Ramo, Schenectady, N. Y., assignors to General Electric Company, a corporation of New York Application July 27, 1940, Serial No. 348,006,,

(on. est-27.5)

10 Claims.

The present invention relates to electronic apparatus for application at high frequencies and makes use of the special properties of a region filled with a space charge which is caused to rotate by the combined action of a uniform magnetic field and a radial electric field.

In a paper published in thePhysical Review for April 1, 1940 (vol. 57, ms. 635-6't1) we have given an analysis of electromagnetic wave propagation in a region filled with a space charge which is caused to rotate in the manner speci- This analysis indicates that under differing conditions, varying types of rotationally propagated waves may be expected to exist in the space-charge-filled region, One predictable type of wave, for example, is that which produces a single node and a single anti-node of charge density at diametrically displaced points in the space charge region. Other modes of operation are variously represented by the existence of different finite numbers of nodes and anti-nodes of charge density.

The theory indicates that for the higher modes of operation the product AH, (in which A represents the free space wave length of the particular wave being generated" and H represents the magnetic field required to produce such wave length) is very much decreased from the values required for lower order waves. Thus. the fol lowing table represents the nature of this change for a particular kind of operating system.

Order of wave *Wave traveling in direction of space charge rotation. t*"t\ Vave traveling in opposition to space charge re a ion.

It is significant to note that the value ).H=-15,100

of a few centimeters), and it turns out that as a result of the relationship stated above the magnetic field strength required to produce such wave lengths is extremely high. Consequently, the application of magnetrons has been quite limited because of the cumbersome magnetic structures needed for their use.

Inaccordance with our present invention practical use is made of the theoretical considerations set forth above by the provision of electrode structures adapted to assure operation of a rotating space charge system in one of the higher modes of wave generation. As the theory indicates, the realization of such modes of operation permits a very great reduction in the magnetic field strength required for generation 01 a particular wave length, and thus leads to more compact and useful forms of apparatus than have heretofore been available in the magnetron cate- A particular arrangement which has been found effective to produce higher order waves includes a hollow cage-like anode structure within which a rotating space charge is produced. The anode structure is made up of several (at least six) mutually spaced vane-like elements which act to stimulate the space charge in the desired manner. With the various vanes conductively connected so that adjacent vanes may act as cooperative components of a standing.- wave system, it proves possible by means of the apparatus specified to generate high frequency oscillations with an applied magnetic field much weaker than has heretofore been considered necessary in thisclass of apparatus.

The features which we desire to protect herein are pointed out with particularity in the appended claims. "I'he invention itself, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a side view in partial section of an apparatus'suitably embodying the invention, Fig. 2 is a transverse sectional view taken on line 3-2 of Fig. 1, Figs. 3 and 4 represent modified forms of electronic device suitable for use in the apparatus of Fig. 1, and Figs. 5 and 6 conjointly illustrate an alternative embodiment of the invention.

Referring particularly to Fig. 1 there is shown an elongated evacuated envelope it, consisting of glass or the like. Within the envelope and extending axially thereof there is provided an electron source in the form of a filamentary cathode M which is supported and supplied with current by means of lead-in conductors it and i3 sealed into the ends of the envolope. Aeoiled spring M connected to one extremity of the filament ll serves to maintain the filament under tension.

Surrounding the filament and generally coaxelements shall be in the shape of thin strips or vanes having their major surfaces lying in radial planes and defining elongated gaps between them. The spacing between adjacent conductive elements is, as appears in the drawings, greater than the thickness of the elements so that the resulting structure comprises a relatively open cagelike arrangement.

In the arrangement shown the vane-like elements it are directly conductively connected at their extremities by means of metal rings is and it in such fashion that adjacent elements are capable of functioning as cooperative components of a resonant transmission line. In this connection each pair of elements may be assumed to constitute a half wave line which is short-circuitecl at its extremities, and for present purposes the length of the line should be correlated to the desired operating frequency of the apparatus as a whole.

Outside the envelope ill and substantially completely enclosing the same there is provided a conductive shield or tank which serves dually as a means for preventing free radiation from the electronic system and as a resonator for assisting the generation of high frequency waves within the interior of the tank. Magnetic coils; it and 25, which closely surround the tank 2i, act when energized to produce a uniform magnetic field extending axially of the device it and especially within the region enclosed by the anode structure of the device.

For the direct current energization of the apparatus there is provided an appropriate voltage source which is illustrated diagrammatlcal ly in Fig. 1 as a battery til. A portion of the battery 28 is used to supply heating current to the filament ii, and the high voltage terminals of the battery are connected between the filament lead-in conductor i3 andan anode lead-in conductor 29, the circuit to the latter conductor being completed through the grounded wall of the tank it.

By the means just specified a radial electric field is created between the cathode filament ii and the surrounding anode structure. This field, in connection with the uniform magnetic field produced by the coils 2t and 25, serves to create within the confines of the anode structure a rotating space charge which is maintained by means of electrons emitted from the cathode.

The sharply defined discontinuities provided in proximity to the space charge by the presence of the thin vanes i6 stimulate or excite the space charge in such fashion as to assure the generation therein of circumferentially propagated waves of a higher order than unity, the nature of wave generation being determined at least in part by the number of vanes employed.

The waves thus developed excite the 'half' wave transmission being confined to the region within the tank 2i, tends to maintain the space within the tank also in an excited condition, and if 'these various components are properly matched in an electrical sense, the whole system may produce sustained high frequency oscillations.

Power may be taken from the system for external utilization by suitable coupling means either of inductive or capacitive character. The particular coupling means illustrated comprises a conductive'loop 32 arranged coaxially about the device it) and having one of its terminals (the terminal 33) connected directly to the wall of the tank 2! (see Fig. 2). The other terminal 3% of the coupling loop becomes the inner conductor of a coaxial element transmission line having as an outer conductor ametal tube 35 which extends. outwardly from the wall of the tank.

A particular advantage of the apparatus above described lies in the fact that the effects described may be obtainedby the use of a much weaker magnetic field than has heretofore been required for the successful operation of devices in the magnetron class. As previously stated herein, this is believed to be a consequence of the fact that the electronic structure employed is of such character as to facilitate or assure the production of higher order waves within the rotating space charge. It has so far proven possible to obtain oscillations of a wave length on the order of 10 centimeters with a magnetic field strength as low as 300 gauss, this being a reduction on the order oi 5 to 1 below the values indicated as necessary by experiments with previously available magnetron devices.

The particular organization of parts shown in Fig. l is, of course, not a necessary attribute of the invention and in. Fig. 3 there is shown an alternative construction which may be employed. In this case the electronic device includes, in common with the device in Fig. 1, an evacuated envelope ii] having a filamentary cathode ti ex-' tending axially thereof. On the other hand, the vane elements 63 which make up the anode structure are open-circuited at their extremities, being conductively connected at their central portions, however, by means of a metallic ring M. With this arrangement the opposed halves of adjacent vanes tend to perform as cooperating elements of a quarter wave transmission line which is short-circuited at one end (i. e. by the ring ti t) and open-circuited at the other. The length of the vanes should, accordingly, be fixed with this consideration in mind.

"in operation, the functioning of the device of Fig. 3 is substantially identical with that of the device of Fig. 1 (except for the differences noted above). It may, therefore, be inserted in place of the latter device in the apparatus of Fig. 1 without any other significant change of the arrangement.

Another structural change which may be made without affecting the fundamental principles of operation of the apparatus pertains to the means employed for creating a space charge and is exemplified by the arrangement of Fig. 4. As in the construction previously described, the operative elements of the device are enclosed within a sealed envelope (identified in this case by the numeral 50). In the new arrangement, however,

"the longitudinally extending filament previously described lsr'eplaced by a n electron source" an l ranged at one end-of the-envelope. This includes ity closed by means of a metal wall 52 which is coated with an appropriate emitting substance, such as alkaline earth material. A heater 58, which is positioned within the cathode and which is energized by means of a heating battery M,

serves to maintain the coated surface of the of the anode by the positive potential applied thereto shall form a uniformly distributed space charge, means are provided for so regulating the electric field distribution as to obtain this result. Such means comprises two pair oi partially acter are known to the art, and, since they form no part of our present invention, will not be discussed in detail herein.

It will be understood that as long as the proper space charge is established within the anode.

structure, the nature oi its origin is immaterial and its action under the combined influence of magnetic and electric fields is of invariant character. Accordingly, subject to minor changes of arrangement made necessary by the modified electrode structure, the device of Fig. i may be substituted in the apparatus of Fig. 1 without changing the functioning oi the apparatus.

In some cases it may be desirable to provide means more compact than the enclosing tanls and associated transmission line illustrated in Fig. 1 for controlling and confining the propagation of energy from the generating source. Una means for accomplishing this end is shown in Figs. 5 and 6 hereof.

Referring particularly to Fig. 5 there is shown an evacuated enclosing envelope it which contains an axially extending filamentary cathode ll. Surrounding the cathode there is provided an anode structure which includes a number of vane-like elements it (see Fig. 6) which have relatively great extension in the radial direction and which ,define wedge-shaped spaces between them. The extremities of the vane-like elements. are conductively connected by means of annular disks it and it which completely close-the ends of the gaps between the elements. The outward openings of these gaps (with the exception of a I single gap) are additionally closed by means of a metallic cylindrical member ll which extends around the outer contour of the anode structure.

' This member is provided with an axially extending opening it which is coextensive with the gap between one pair of adjacent varies and which permits the space between such vanes to be freely externally exposed.

In the use of the apparatus the cathode ll is appropriately energized and is maintained at a negative potential with respect to the anode structure by means 01' a suitable voltage source (not shown). Magnetic coils and 8|, which are respectively positioned about the ends of the envelope 10, provide a uniform axial magnetic field for causing rotation of the space charge developed about the cathode ii.

The vanes 13' are quite similar to the vanes i6 scribed, adjacent vanes serve. by virtue of their distributed constants, as resonant structures adapted to be maintained in excited condition by reaction with the space charge. The whole system is, therefore, suitable for the creation and maintenance of high frequency oscillations.

As a result of the presence of the cylindrical shield ill the electronic system is effectively sealed against radiation except for the opening it. Consequently, such radiation as occurs must take place through this opening and will therefore he strongly directional in character. As a result of this fact the arrangement described is sultableior use as a directional transmitter of high frequency waves.

While the invention has been described by reference to particular embodiments thereof, it will be understood that numerous modifications may be made therein by those skilled in the art without departing from the invention. We, therefore, aim in the appended claims to cover all such equivalent variations as come within oluctive elements which are circumierentially spaced to provide gaps between them, the spacing between adjacent elements being at least as great as the thickness of the elements, means for conductively interconnecting the various elements to assure the functioning of adjacent elements as components of a standing wave system, means for providing electrons within the anode structure to produce a space charge therein, and means for producing a magnetic field axially of the structure to cause rotation of the bination of a hollow cylindrical anode structure constituted of at least six axially extending conductive elements which are circumferentially spaced to provide gaps between them, the spacing between adjacent elements being at least as great as the thidkness of the elements, means including a conductive ring for electrically connecting the various elements to assure the functioning of adjacent elements as components of a standing wave system, means for providing electrons within the anode structure to produce a space charge thereimand means for producing a magnetic field axially of the structure to cause rotation of the said space charge and to facilitate production therein of circumferentially propagated waves.

' means for producing a magnetic field axially of the structure to cause rotation of the said space charge and to facilitate production therein of circumferentially propagated electromagnetic waves.

4. Electronic apparatus comprising the combination of a plurality of thin-edged elongated conductive elements which are arranged to form a hollow cage-like structure and which are mutually spaced to provide sharply defined gaps between them, means for directly conductlvely connecting the various elements to assure the functioning of adjacent elements as components of a standing wave system, means for providing electrons axially of the anode structure to produce space charge within the structure, and means for producing a magnetic field axiallyof the structure to cause rotation of the said,- space charge and to facilitate production therein of circumferentially propagated waves.

5. Electronic apparatus comprising the combination of a hollow cylindrical anode structure constituted of at least six elongated vane-like members having their major surfaces in radial planes, said vane-like members being mutually spaced to provide gaps between them, means for directly conductively connecting the various elements to assure the functioning of adjacent ele ments as components of a standing wave system, means for providing electrons axially of the anode structure to produce space charge within the structure, and means for producing a magnetic field axially of the structure to cause rotation of the said space charge and to facilitate production therein of circumferentially propagated waves.

6. Electronic apparatus comprising the combination of a hollow. cylindrical anode structure constituted of at least six conductive vane-like elements which are circumferentially spaced to provide gaps between them, means for connecting the various elements to assure the functioning of adjacent elements as components of a standing wave system, means for providing electrons within the anode structure to produce space charge therein, means for producing a magnetic field axially of the structure to cause rotation of the said space charge and to facilitate production therein of circumferentially propagated waves, and means for preventing undesired radiation of wave energy from the structure except through the gap existing between a selected pair of vanes.

7. Electronic apparatus comprising the combination of at least six elongated vane-like members grouped about a common axis to form a hollow cylindrical anode structure, said vanelike members being mutually ,spaced to provide gaps between them and having their major surfaces in radial planes, means for conductively connecting the extremities of the various elements 'so as substantially to'close the ends of for providing electrons within the anode structure to produce space charge therein, and means for producing a magnetic field axially of the structure to cause rotation of the said space charge and to facilitate production therein of circumferentially propagated waves, there being an opening in the surface of the said shield to permit radiation therethrough of wave-energy generated within said anode structure.

8. Electronic apparatus comprising the combination of at least sixelongated vane-like members grouped about a common axis to form a a faces in radial planes, means connecting the extremities of the said member so as substantially to close the ends of the anode structure, a cylindrical shield in contact with the outer edges of the said vane-like members and enclosing the anode structure, means for providing electrons within the anode structure to produce space charge therein, and means for producing a magnetic field axially of the structure to cause rotation ofthe said space charge and to facilitate production therein of circumferentially propagated waves, there being an opening in the said,- cylindrical shield which is substantially coextensive withthe gap between one pair of adjacent" vanes to permit the radiation therethrough of wave-energy developed within the anode structure.

9. Electronic apparatus comprising the combination of a hollow cylindrical anode structure constituted of at least six conductive elements which are circumferentially spaced to provide. gaps between them, the spacing between adjacent elements being at least as great asthe thickness of the elements, means for connecting the various elements to assure the functioning of adjacent elements as components of a standing wave system, means for providing electrons within the anode structure to produce a space charge therein, means for producing a mag netic field axially of the structure to cause rotation of the said space charge and to facilitate production therein of circumferentlally propagated waves, and shielding means for preventing undesired radiation of wave-energy from the structure.

10. Electronic apparatus comprising the combination of a hollow cylindrical anode structure constituted of at least six 'circumferentially spaced vane-like elements consisting of conductive material, the major surfaces of the various elements being in radial planes so that adjacent elements define wedge-shaped spaces between them, means for connecting the various elements to assure the functioning of adjacent elements as components of a standing wave system, means for providing electrons within the anode structure, to produce a space charge therein, means for producing a magnetic field axially of the structure to cause rotation of the said space charge and to facilitate production therein of circumferentially propagated waves, and conductive shielding means extending between the outer edges of at least certain ones of the vanethe anode structure, a cylindrical shield 'perimetrically enclosing the anode structure, means like elements for preventing undesired radiation of wave energy through the openings between I I 

